Chemical synthesis strategy for increasing the stability and biocompatibility of chemically-synthesised therapeutic oligonucleotides

Challenge

DNA and RNA are biomolecules that are fundamental to all known forms of life. In recent years, many successful attempts have been made to harness the myriad functions of nucleic acids and apply them in the fields of medicine, forensics and genetic testing. In general, these applications utilise DNA and/or RNA in its native chemical form, which is produced through well-established solid phase synthesis methods. These require single nucleotides to be added sequentially making them highly time-consuming. However, certain emerging applications require longer, more robust, and more complex nucleic acid structures, with greater customisability, so new synthetic approaches are required. To meet the demand created by breakthroughs, such as the development of therapeutic oligonucleotides, researchers have sought novel chemical ligation techniques allowing for the combination of smaller strands of DNA and RNA, to produce larger nucleic acid structures. One such ligation technique utilises azide-alkyne “Click” chemistry to generate a biocompatible linking triazole moiety, however the presence of such groups in the DNA/RNA backbone renders the resulting biomolecules unable to bind (Watson-Crick base pair) to complementary DNA/RNA sequences as efficiently. The efficiency, selectivity and strength of this binding is often crucial to its application.

Technology

Researchers at the University of Oxford have developed a ligation methodology which exploits the biocompatible triazole linkages in combination with locked nucleic acids (LNAs) to yield oligonucleotides, which display significantly higher binding affinities and greater resistance to enzymatic degradation. In addition, reagents have been developed which allow for facile incorporation of this functionality into traditional solid phase synthesis methods. We believe the main benefits of the Oxford Triazole-LNA approach are as follows:

• Over 20% increase in DNA:RNA duplex stability compared to triazole alone

• Facile readthrough of DNA by DNA polymerases

• Less susceptible to enzymatic degradation than native DNA/RNA

• Synthesis uses commercially available materials and solid phase techniques

Commercial Opportunity

The global nucleic acid therapeutics market is expected to record a value of US$7.23 billion in 2024. Nucleic acid therapeutics have emerged in recent years to yield extremely promising candidates for drug therapy to a wide range of diseases. The high prevalence of various monogenetic diseases is leading to the rising application of various nucleic acid therapeutics, which is likely to help in its market growth in future. Owing to the sudden outbreak of COVID-19, scientists are evaluating various biomolecules and synthetic inhibitors against COVID-19; where the nucleic acid-based molecules may be considered as potential drug candidates, which is posing as an opportunity for the market growth of the nucleic acid therapeutics globally. Technologies such as this LNA  which increase the speed of translation and strength of binding in novel chemical ligation techniques are critical components in enabling the industry to fully realise the potential of nucleic acid therapeutics.

Development Status

Pre-clinical, in vitro currently.

Patent Situation

This technology is the subject of two patent applications, which are each approaching grant in the US. US-2019-0023732-A1 (Triazole LNA Dinucleotides) and US-2019-0015439A1 (Antisense Oligonucleotides containing Triazole and LNA).

Further Reading

pubs.acs.org/doi/pdf/10.1021/acsomega.8b01086